PD pumps with a common gearbox module and varying capacities and easy access to mechanical seals

Abstract

Rotary lobe pump and circumferential piston pump designs are disclosed where the drive and driven shafts are detachably connected to their respective rotors. The rotors are disposed in a pump or rotor casing, which is sandwiched between a head cover and a gearbox. The drive and driven shafts pass through mechanical seal assemblies, which are sandwiched between the first and second rotors and the gear box respectively. The seal assemblies can be serviced or replaced by simply removing the head cover and removing the rotors from the drive and driven shafts. The pump casing does not need to be removed to replace or service the seal assemblies. Further, the capacities of the disclosed rotary lobe and circumferential piston pumps can be modified without changing the gearboxes or shaft length. To modify a pump capacity, all that needs to be changed are the rotors, the pump or rotor casing and, in some designs, the head cover or cover plate. In some designs, the cover plate is universal to the gearbox so that only the rotors and pump casing need to be changed to modify the pump capacity.

1. A positive displacement pump comprising:
 a drive shaft passing through a gearbox and being detachably connected to a first rotor, the drive shaft being rotatively coupled to a driven shaft, the driven shaft being detachably connected to a second rotor, 
 the first and second rotors being disposed in a pump casing, the pump casing being disposed between a head cover and the gearbox, 
 the drive and driven shafts passing through first and second mechanical seals respectively that are sandwiched between the first and second rotors and the gear box respectively, 
 the first and second rotors each comprise a central hub for accommodating the drive and driven shafts respectively, each central hub comprising a distal end directed towards the head cover and a proximal end directed towards the gear box, the proximal ends of the central hubs of the first and second rotors each being connected to an annular section that connects its respective proximal end to at least one radially outwardly directed wing, 
 the first and second rotors each comprise an annular slot between their respective central hubs and its respective wing, the head cover comprising first and second cup-shaped structures with first and second cylindrical walls, and the annular slots of the first and second rotors receiving the first and second cylindrical walls of the head cover respectively, 
 wherein removal of the head cover and the first and second rotors from the drive and driven shafts respectively provides access to the first and second mechanical seals. 
 
     
     
       2. The pump of  claim 1  wherein said access to the first and second mechanical seals includes an ability to remove the first and second seals without removing the casing. 
     
     
       3. The pump of  claim 2  wherein the casing comprises a rear wall with first and second openings for accommodating the drive and driven shafts respectively, and
 the annular sections of the first and second rotors are each connected to a rearwardly extending the outer hub that is accommodated in first and second recesses disposed in the rear wall of the casing. 
 
     
     
       4. The pump of  claim 3  wherein the first and second recesses are disposed along outer peripheries of the first and second openings respectively in the rear wall of the casing. 
     
     
       5. The pump of  claim 3  wherein the first and second mechanical seals are at least partially disposed within the rearwardly extending outer hubs of the first and second rotors respectively. 
     
     
       6. The pump of  claim 1  wherein the first and second rotors each comprise a central hub for accommodating the drive and driven shafts respectively, the central hubs of the first and second rotors being connected to annular sections that are each disposed between its respective central hub and at least one radially outwardly directed wing of its respective rotor. 
     
     
       7. The pump of  claim 6  wherein the rearwardly extending outer hubs of the first and second rotors are journalled into the rear wall of the casing. 
     
     
       8. The pump of  claim 1  wherein the pump is one of a rotary lobe pump or a circumferential piston pump. 
     
     
       9. A positive displacement pump comprising:
 a drive shaft passing through a gearbox, the drive shaft being detachably connected to a first rotor, 
 the drive shaft being rotatively coupled to a driven shaft, the driven shaft being detachably connected to a second rotor, 
 the first and second rotors being disposed in a pump casing, the pump casing being disposed between a head cover and the gearbox, 
 the first and second rotors being accommodated in first and second cavities respectively in the pump casing, 
 the first and second rotors each comprise a central hub for accommodating the drive and driven shafts respectively, each central hub comprising a distal end directed towards the head cover and a proximal end directed towards the gear box, the proximal ends of the central hubs of the first and second rotors each being connected to an annular section that connects its respective proximal end to at least one radially outwardly directed wing, 
 the first and second rotors each comprise an annular slot between their respective central hubs and its respective wing, the head cover comprising first and second cup-shaped structures with first and second cylindrical walls, and the annular slots of the first and second rotors receiving the first and second cylindrical walls of the head cover respectively, 
 wherein a capacity of the pump is varied by changing the first and second rotors and pump casing without changing the gearbox. 
 
     
     
       10. The pump of  claim 9  wherein the head cover must also be changed to change the capacity of the pump. 
     
     
       11. The pump of  claim 9  wherein the drive and driven shafts pass through first and second mechanical seals respectively that are sandwiched between the first and second rotors and the gear box respectively, and
 wherein removal of the head cover and the first and second rotors from the drive and driven shafts respectively provides access to the first and second mechanical seals. 
 
     
     
       12. The pump of  claim 9  wherein the first and second rotors each comprise a central hub for accommodating the drive and driven shafts respectively, the central hubs of the first and second rotors being connected to annular sections that are each disposed between its respective central hub and at least one radially outwardly directed wing of its respective rotor. 
     
     
       13. The pump of  claim 12  wherein the casing comprises a rear wall with first and second openings for accommodating the drive and driven shafts respectively, and
 the annular sections of the first and second rotors are each connected to a rearwardly extending the outer hub that is accommodated in first and second recesses disposed in the rear wall of the casing.